Floor standing microscopes with user-positionable arms are used in many ophthalmic medical procedures, e.g. ophthalmic surgery. Conventional ophthalmic microscopes may utilize a hydraulic arm locking system that may become unreliable due to fluid leaks. Alternative arm locking systems may suffer from positioning backlash, noisy operation, or excessive friction during use. Accordingly, there is a need in the art for an ophthalmic surgical device (such as an ophthalmic microscope) that has a user-positionable arm with improved reliability, reduced backlash, or smoother or quieter operation.